Have you noticed a slimy film inside your pet’s water dish? What if I told you that it is dangerous to both you and your pets? And simply cleaning out the water dish properly could decrease your pet’s risk for diseases?

The slimy film is called biofilm. Biofilm is any group of microorganisms in which cells stick to each other and often adhere to a surface. The materials that make up a biofilm can be bacteria, other microorganisms, algae, and fungi.

Before cleaning
After cleaning

How does it form?

Formation of a biofilm begins with the attachment of free-floating microorganisms to a surface. Materials can be picked up from your pet’s food, ball, bone, toys, and anything else he licks or puts in his mouth (which is usually everything). These materials are released into the water bowl every time he drinks. Bacteria then release a slippery, yet sticky substance that attaches to a surface. Then bacteria, moisture and nutrients combine to make the perfect environment in which to live and multiply.

What’s the harm?

Biofilms usually contains many different species of bacteria such as Salmonella, E.coli, Listeria sp., Staphylococcus sp., etc. They may also contain microorganisms, algae, and fungi. Though your pet’s immune system can fight off small amounts of these bacteria, a large growth in a biofilm can be harmful, especially when exposed continuously.

Periodontal disease is a frequent and often overlooked problem for dogs & cats. Plaque in the mouth is a more commonly known biofilm. The bacteria in plaque and tartar from the mouth enter the blood stream traveling to organs casing and damaging them over time. Biofilm has also been thought to cause or exacerbate other medical issues such as ear and urinary tract infections and kidney disease (especially in cats).

According to the National Sanitation Foundation (NSF), pet bowls come in fourth on the list for places in the home that contain the most germs. Your pet may not be the only one exposed to these hazards, but also you and your family. Small children may play in a pet’s water bowl, exposing them to the bacteria in the biofilm. While cleaning the bowls, you may encounter the bacteria and spread it to dish rags, sponges, utensils, dishes, and anything else in and around your kitchen sink.

Biofilm gives off an odor which can be offensive to both humans and pets. Since pet’s sense of smell is far more sensitive than humans, the odor may deter them from drinking their water. Lack of hydration can lead to or worsen other medical conditions.


  • Type of Bowl- Plastic bowls scratch easily and may be porous, allowing bacteria a place to hide and making it harder to sanitize. Glass and stainless steel bowls are better, but still can form a biofilm. Using a clear or white bowl can make it more noticeable when the biofilm forming.
  • Clean the bowls & toys regularly– Wash pet food bowls after every meal and the water bowls at least once a day. Keep a close eye on any outdoor water bowls, especially in hot weather, which provides a perfect environment for algae and bacteria to grow. Clean all washable toys regularly either in the washing machine or dishwasher.
  • Pick the correct spot- Do not wash them in the kitchen sink or bathtub. You could transfer germs to your dishes, utensils, food, or yourself. A utility sink would be preferable.
  • Scrub first– Spraying cleaner on it won’t work. Biofilm needs to be physically broken up for a disinfectant to work well on the bacteria. Use a clean rag to wipe the dish before you disinfect and do not use it on other dishes after. An abrasive scrubber may leave scratches in the material in which bacteria can easily cling and hide.
  • Disinfect with bleach– After scrubbing, clean with a diluted bleach solution (1 Tbsp bleach to 1 gallon of water. Let bowl soak for a few minutes. Be sure to rinse well. Do not use bleach on aluminum bowls.
  • Use the dishwasher– An easy and effective option would be to run the bowls through the sanitizing setting on your dishwasher. As long as you use the sanitizing cycle, you can wash pet bowls with your other dishes.